Armor-plate and other article of steel.



P. GIOLITTI.

ARMOR PLATE AND OTHER ARTICLE OF STEEL.

APPLICATION FILED APR. 10. 1909v 94:6,428, Patented Jan. 11, 1910.

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UNITED "STATES PATENT orrron.

FEDERICQ GIOLITTI, 0F ROME, ITALY, ASSIGNOR TO SOCIETA ANONIMA ITALIANA GIO.

ANSALDO ARMSTRONG & 0., OF GENOA, ITALY.

ARMOR-PLATE AND OTHER, ARTICLE OF STEEL.

Specification of Letters Patent.

Original application filed August 31, 1908, Serial No. 451,053. Divided and this application filed April 10,

1909. Serial No. 489,142.

To all whom it may concern:

Be it known that I, FEDERICO GIoLrrrI, a subject of the King of Italy, and residing at 35 Via Palestro, Rome, Italy, have invented certain new and useful Improvements in Armor-Plates and other Articles of .Steel and Alloys of Steel, of which the following is a specification.

This invention relates to improved armor plates and other articles of steel or alloys of steel for ships and other uses.

Armor plates and other articles of steel or alloys of steel'having an outer zone which is more highly carbureted than the remainder of the article by means of a process of cementation at a temperature above 1000 degrees Celsius, have been produced hitherto by heating the article either in contact with a powdered or granular substance capable of giving up carbon, or in an atmosphere of gaseous carbids of hydrogen or of vapors of liquid carbids of hydrogen, with or without an admixture of nitrogenous substances (such as the va ors of ammoniacal salts, cyanids, etc.). he carbureted zones produced by those methods are always characterized by the fact that their outer layers are highly carbureted and that the contained carbon diminished gradually in the deeper layers. 1

It has been hitherto impossible to produce a cemented zone in which the superficial or. outer layers contain less than from 0.8 to 0.9 per cent. of carbon. In fact these layers contain generally more than 1 per cent. in those cases where the depth of the cementation exceeds 15 to 20 millimeters. It has also been found impossible by known methods to producencemented layers having a uniform or approximately uniform percentage of carbon throughout a thickness equal to one-half or two-thirds of the total thickness of the carbureted zone. This is due to the circumstance that all the known methods produce cemented zones in which the percentage of carbon diminished continuously toward the inner layers, rapidly at first and then slowly. I

Now the present invention has for its object to produce an article of steel or alloys of steel having a cemented zone of any desired thickness containing-a percentage of carbon which shall not exceed at any point Patented Jan. 111, row:

here, namely that by avoiding a high car-- burization of the surface layer of the cemented steel articles, it is possible also to eliminate completely the brittleness of the surface layer. This is of particular importance in armor plates, and especially in plates made from chronic steel. But the advantages are much greater.

The above mentioned results are obtained by utilizing the following reversible reaction:--

. 2 OO=GO +O Car- Car- Carbon bonic bon.

monoxid. acid. i This reaction takes place in a different degree and at varying speeds according to the conditions of temperature and pressure and according as there are other substances present that are capable of reacting with one or more of the three substances between which the said reaction takes place. This is in accordance with perfectly defined chemical laws.

When carbon monoxid is heated by itself it becomes decomposed in accordance with the above stated equation until a determined proportion has been reached between theresulting carbonic acid and the carbon monoxrd that is not yet decomposed. As soon as t h1s proportion (which varies with the variation of the temperature and pressure of the gases) is reached, the above stated reaction beg-ins to. take place at the same speed but in the inverse sense, between the solid carbon and the carbonic acid'until a state of equilibrium is reached. Now, on the contrary when carbon mon'oxid is heated in the presence of an article of steel or iron at a temperature v I 's'ius) at which the iron (gamma lron) dissolves solid carbon as it is being formed, the

(exceeding 900 degrees Celinverse reaction which should produce equilibrium (and stop the decomposition of the carbon monoxid) no longer takes place, as in the first mentioned case, between the carbonic acid and free carbon but between the carbonic acid and the carbon dissolved in the gamma iron and therefore the speed of this reaction will depend also on the concentration of the carbon dissolved in the iron, that is to say, on the percenta e of carbon in the cemented layer. Inverse y by suitably regulating the speed of renewal of the carbon monoxid, the temperature and pressure a determined and constant concentration of the carbon dissolved in the iron, that is to say a determined percentage of the carbon in the cemented layer can be obtained.

The following example is given for the purpose of illustrating the nature of the invention. It is assumed that it is desired to produce a carbureted outer layer in a mild steel having, for instance the following composition Carbon 0.06 per cent. Manganese 0.25 per cent. Silicon 0.01 per cent. Sulfur 0.04 per cent. Phosphorus 0.03 per cent.

It is assumed further that it is desired that the layer which is to have a thickness of 22 millimeters shall not contain at any point, not even at the surface, more than 0.4 per cent. of carbon, and that the percentage of its contained carbon shall be approximately uniform throughout the first 15 millimeters of thickness. As will be perceived, the percentage of carbon contained in the cemented layer, chosen for this illustration, is so low that it would be impossible not to exceed it by the ordinary processes of cementation. In order to obtain this special cemented layer the article to be cemented is heated in a cementation or other furnace for about 40 hours at 1100 degrees 0., in an atmosphere of carbon monoxid which is being renewed by introducing into the cementation chamber during about every hour a cubic meter of carbon monoxid for each square meter of surface of the article to be cemented.

The carbon monoxid which is required for the cementation may be readily obtained by passing a current of carbonic acid over coke heated above 1200 degrees C. in metal tubes or vessels composed of refractory mater1a s.

The carbon monoxid which has already been caused to give .up its carbon to the steel to be cemented, may be regenerated and then used over again, by being passed over coke heated to a temperature exceeding 1200 de 'grees, 0., so as to re-convert into carbon monoxid the small quantity. of carbonic acid eaenae that has been formed during the cementation by the hereinbefore stated reaction.

In cases whereit is desired to obtain a uniform carbureted layer containing a higher percentage of carbon, for instance, from 0.6 to 0.7 per cent., the conditions stated in the preceding example must be varied acording to one of the following four methods 1. By lowering the temperature (but not below 900 degrees C). The herein above stated reaction is exothermic and is' therefore promoted by lowering the temperature).

2. By increasing the pressure of the carbon monoxid.

3. By increasing the amount of carbon monoxid which is caused to pass during a given time, around the steel articles to be cemented.

4. By mixing with the carbon monoxid varying quantities (to be determined by experlment in such particular case) of gaseous carbids of hydrogen, or vapors of'liquid carbids of hydrogen for the purpose of regenerating (more or less completely and rapidly according to their quantity and quality) the carbon monoxid which has been converted into carbonic acid 'during the cementation process, the carbids of hydrogen acting as reducers by means of their carbon and their hydrogen, and converting the carbonic acid back into carbon monoxid in accordance with the two equations .By employing one of these methods, or two or three of them in combination, or all four of them, the articles of steel or alloys of steel can have formed in them carbureted layers of any desired thickness containing any desired percentage of carbon between a minimum of 0.2 per cent. and a maximum of 1.3 per cent. The article thus treated may be subjected to one of the ordinary processes of cementation in order to produce an external layerof-a high degree of carburization, or to one of the ordinary refining processes for the purpose of produc ing an external decarburized layer, or to a refining and to a cementing process in succession. The article may also be subjected to ordinary thermic treatments such as hardening, tempering, annealing, or to mechanical treatment by means of a press, rollin mill, hammer etc., adapted to, impart to it the desired shape and properties.

The accompanying drawing is diagrammatic and illustrates in vertical section (by way of example only) a form of furnace 125 suitable for carrying out the present improvements.

E is a closed chamber containing the ar- -l1l01 plates 1*, G, H to be cemented or carburized.

I is a pipe for delivering carbon monoxid into the chamber E, and P is a pipe through which the carbon monoxid escapes after circulating' in said chamber.

C, C are fire grates for burning solid fuel for heating the chamber E from the outside.

D, D are hoppers closable at. both ends for charging fuel on to the fire grates C.

A, A are mains for delivering compressed air underneath the fire grates C.

B, B are valves for regulating the flow of the air delivered underneath the fire grates C for raising or lowering the temperature of the furnace.

L is a pipe for supplying carbon monoxid to the pipe I.

Q is a valve for regulating the flow of carbon *monoxid through the pipe L.

N is a pipe for supplying hydrocarbons into the pipe I to be mixed with the carbon monoxid enterin from pipe L.

M is a valve or re lating the quantity and pressure of the ydrocarbons flowing through the pipe, N.

Having now described my invention what I claim as new and desire to secure by Letters Patent is 1. As a new article of manufacture, an armor plate or other article of steel or alloys of steel, having a carburized zone of any desired thickness containing a percentage of carbon always under 1.3 per cent., and being uniform and constant throughout a depth not less than one-half of the total thickness of the carburized'zone, as set forth.

2. As a new article of manufacture, an armor plate-or other article of steel or alloys of steel, having a carburized zone of any desired thickness containing determined percentage of carbon lying between 0.2 per cent. and 1.3 per cent., and being uniform and constant throughout a depth not less than one-half of the total thickness of the carburized .zone, as set forth.

In testimony whereof, I aflix my-signature in presence of two witnesses.

' FEDERICO GIOLITTI.

Vit-nesses:

G. B. ZANARDO, VINGENTO DE No'rELLI. 

